[PATCH v3 01/17] mm, compaction: don't isolate PageWriteback pages in MIGRATE_SYNC_LIGHT mode
From: Vlastimil Babka
Date: Fri Jun 24 2016 - 05:55:10 EST
From: Hugh Dickins <hughd@xxxxxxxxxx>
At present MIGRATE_SYNC_LIGHT is allowing __isolate_lru_page() to
isolate a PageWriteback page, which __unmap_and_move() then rejects
with -EBUSY: of course the writeback might complete in between, but
that's not what we usually expect, so probably better not to isolate it.
When tested by stress-highalloc from mmtests, this has reduced the number of
page migrate failures by 60-70%.
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
---
mm/compaction.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index c611b8a42023..b7b696e46eaa 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1204,7 +1204,7 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
struct page *page;
const isolate_mode_t isolate_mode =
(sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) |
- (cc->mode == MIGRATE_ASYNC ? ISOLATE_ASYNC_MIGRATE : 0);
+ (cc->mode != MIGRATE_SYNC ? ISOLATE_ASYNC_MIGRATE : 0);
/*
* Start at where we last stopped, or beginning of the zone as
--
2.8.4